Signal generators, such as phase-locked loops PLL, are used in a wide range of applications requiring source signals for performing different tasks. For instance, a PLL may be used to provide a source signal to a wireless communications system.
In addition to synthesizing the frequency at which a signal is to be transmitted and received, a PLL can also be used for performing frequency and phase modulation of the carrier frequency. To provide phase modulation of the carrier frequency, current PLLs require multiple steps. One method requires first converting a phase modulated input signal to a frequency modulated input signal by taking the derivative of the phase, and then using so called two-point frequency modulation to modulate the PLL carrier frequency. Another method is based on generating two signals with 90 degree phase shifts, referred to as I and Q signals. Then phase modulation can be achieved by adding up the I and Q signals with different amplitude.
These approaches impose very strict restrictions on the performance of the PLL. In turn, this increases the power consumption and the footprint of a semiconductor device that includes such a PLL. It is an object of the disclosure to address one or more of the above-mentioned limitations.